The invention relates to preparations based on water and/or organic solvents and their use as a finish on flat materials.
It is known that flat materials are finished using water-based or solvent-based preparations of silicone oils, paraffins, fluorocarbon (FC) polymers and other additives that endow the finished flat material with particular hydrophobic effects in order that the flat material may in use be able to meet the challenge of exposures to rain, splashed water or moisture from other sources. Tent fabrics, for instance, are treated with aqueous emulsions of paraffins, metal soaps and also silicic acid salts of polyvalent metals in order that the textile surface may be rendered impervious to rain or splashed water. Preparations of this kind are also used for treating paper, again in order to improve the hydrophobic properties. German Auslegesschrift DE-AS 1001965 discloses using reaction products of basic metal salts of high molecular weight fatty acids or resin acids and low molecular weight di- or polyisocyanates to be applied onto textiles from organic solvents.
Common to all these known uses is that, after their treatment with the chemicals mentioned, the flat materials cannot be washed or subjected to other cleaning measures to remove any soiling. However, where the substrate is such that cleaning operations cannot be avoided, a dramatic deterioration in the water-repellent properties is observed. This disadvantage can to some extent be compensated by refreshing the hydrophobicity by aftertreatment with suitable hydrophobicizing agents, in which case the chemicals employed will usually have the same or similar chemical bases as the initial finish.
State of the art wovens are widely used in sports and leisure wear, but also for articles in the military or firefighting sector or for other protective clothing. Articles of this kind soil very quickly, especially when intensively used, and therefore are subjected to frequent washing. Washing is typically accomplished using laundry detergents in industrial or household washing machines or by a hand wash. In all washing operations, the flat material is not only wetted by the detergents used but also subjected to a more or less severe mechanical stress due to flexing, wringing and compressing. The conjoint action of laundry detergents and mechanical forces cause substantial detachment of the applied finishes from the flat materials and, after drying, the substrates will possess only moderate water repellency if any. Refreshing the hydrophobicity by spraying or application in the washing machine or similar methods of application is not satisfactorily possible with the impregnating products currently on the market, since the achievement of good hydrophobicity would require that the treated sheet, after it has been dried, be heated to above the melting point of the waxes used in order that the wax particles may be caused to coalesce and hence create a continuous, perfectly hydrophobic film of wax.
It is therefore a prerequisite in relation to the articles mentioned that, as well as providing good initial hydrophobicity, the finish should also be durable to multiple washes. Preparations designed to ameliorate the lack of durability to washing operations were therefore developed early on. For instance, DE-B 1 017 133 describes hydrophobicizing agents prepared by mixing a condensation product of hexamethylolmelamine hexamethyl ether, stearic acid, stearic acid diglyceride and triethanolamine with paraffin. The resulting products are flaky or lumpy and are converted before use into an emulsion form which is appliable from aqueous liquors by melting with hot water or steam and adding acetic acid.
However, the flat materials and fibrous materials endowed therewith have been observed to suffer a distinct harshening of their hand characteristics due to the relatively high add-on, the chemical character of the preparation and especially due to the crosslinking of the fatty acid modified methyloltriazine compound with itself and with the functional groups of natural-based substrates. True, by virtue of this type of reaction, cellulosic substrates, such as cotton or viscose for example, do possess durability to multiple washes, but on lightweight, textile materials built of synthetic fibres of the kind preferentially used for equipping sports and leisure articles, the fibre morphology and also the substantial absence of functional groups mean that it is impossible for a crosslinking reaction to take place to the same extent as in the case of cellulosic articles, which is why the wash durabilities are insufficient. In addition, the harshening is felt to be unnatural and therefore thus finished textiles lack consumer acceptance.
A further, significant disadvantage of the finish described has come to light with the use of these products in commercial practice in that the preparations have to be made at the finisher's from the anhydrous, 100% melt only immediately before use. This is necessary because, owing to the high reactivity of the methylolaminotriazine compound in the aqueous emulsions having high acetic acid contents, a crosslinking reaction may take place within the emulsion particle that not only reduces the reactivity with the textile substrate but also leads to cross-links and agglomerations between the emulsion particles and hence to extreme increases in viscosity. This is the same reason why the preparation when stored for a prolonged period in anhydrous flake, block or prill form, i.e. prior to the emulsifying step, will lose its hydrophobic effects and become increasingly difficult if not impossible to emulsify. The aqueous emulsions likewise possess only limited stability and have to be used up rapidly before reactivity has been reduced to an unacceptable level. It is because of this behaviour that there are hitherto no known ageing-resistant emulsions of the composition described, despite the altogether positive wash durability profile.
Another disadvantage with such preparations is the complicated way the emulsion is made from the flakes. Under present day conditions, frequently involving untrained staff, this constitutes an unacceptable safety risk in textile finishing operations. Moreover, the application process inevitably gives rise to emissions of formaldehyde from the methylolaminotriazine compound and of acetic acid which given today's ecological standards can cause difficulties on account of the noncompliance with emission thresholds.
On the state of the art wovens, especially those composed of synthetic materials, the object described can be achieved in a superior manner through the use of water-based or solvent-based FC polymers. For instance, EP 0 325 918 B1 describes preparations which consist of polyurethanes modified with perfluoroaliphatic groups, and which provide good oil and water repellency on textile substrates coupled with good softness and also satisfactory wash durability. EP 314 944-A- recommends formulations of FC polymers with polyethylene and modified polysiloxanes as providing a particularly smooth, soft hand.
WO 00/29663 A2 describes preparations for durable finishing of fibre which contain reaction products of polyisocyanate-functional compounds with silicone-free and/or silicone-containing softeners and, according to the examples, preferably comprises a hydrophilicizing residue.
Owing to the fact that FC formulations provide not only hydrophobic and oleophobic effects which are durable to washing but at the same time also a good fabric hand, such compounds are currently deemed, especially with regard to use on synthetic flat materials, to be suitable products for the goal to be achieved. The disadvantage with preparations based on FC polymers is their relatively high cost, which is due to the synthesis of FC polymer involving numerous steps, some of which are energy intensive. Moreover, recent studies suggest that FC polymers synthesized by electrofluorination may contain a small amount of by-products whose eco-toxicological properties have not as yet been fully investigated. Although such by-products are not present in the market-dominating FC polymers, which are prepared by telomerization, it cannot be ruled out that the public will take an adverse view of FC polymers as a whole. WO 99/14422 A1 describes preparations for treatment of fibrous substrates which, as well as obligatory FC compounds, comprise the condensation product of a polyisocyanate with a diol and an isocyanate-blocking agent. This condensation product is structurally different from component (2) claimed herein.
The altogether good overall performance level of FC polymers notwithstanding, it is to be noted that, after washing operations, there is a marked reduction in the hydrophobic and oleophobic effects due to deorientation of the active FC moieties on the polymer molecules unless a thermal treatment is carried out to effect a reorientation. Consequently, thus treated flat materials require a heat treatment after washing in order to revitalize the desired effects. For instance, ironing or at least tumble drying at temperatures >80° C. is a prerequisite for good phobic properties.